The present invention relates to an energy converter in a restraining system for vehicle occupants, comprising a tubular converter body of plastically deformable material and a pair of rollers which on two symmetrically opposite sides are arranged with their axes perpendicular to the axis of the tubular converter body.
The purpose of such an energy transformer or converter is to diminish load peaks in a safety belt system which occur during the forward displacement of a vehicle occupant in a vehicle collision. The use of such an energy converter is particularly effective in combination with a belt pretensioner which eliminates the belt slack before the forward displacement of the vehicle occupant begins. An adequate movement travel is then available for the forward displacement of the vehicle occupant and the simultaneously occurring energy transformation.
Such an energy converter, which is also referred to as a force limiter, is described in EP 0 422 410 A1. It consists of a cylinder of plastically deformable material in which a rod is received which projects at its one end out of the cylinder and its other end defines a free space in which a plurality of roller bodies are accommodated. The outer diameter of, the ring arrangement formed by the roller bodies is greater that the inner diameter of the cylinder bore. Under a high tensile load between the cylinder and the rod the roller bodies penetrate into the material of the cylinder wall, performing deformation work with formation of longitudinal grooves; due to this work a high amount of energy is transformed and load peaks in the belt system are diminished.
The limitation of the load peaks occurring in the belt system which can be achieved with such an energy converter makes a substantial contribution to the reduction of the risk of injury, as can be proved with the aid of load measurements on so-called dummies. It has however been found that although the load peaks in the belt system can be limited by such an energy converter, they cannot be avoided.